This invention relates to a method and apparatus for providing information, such as destination and vehicle function information to an automatic guided vehicle (AGV). The invention is intended specifically for use with AGV systems of the type which have another primary AGV guidance system. The guidance system may be an electro-inductive system wherein the vehicle senses and following an electromagnetic field generated through a wire in or on a floor which defines the AGV path. Another guidance system suitable for use in combination with the invention according to this application would be an optical guidance system wherein a light detector on the AGV guides the AGV from point to point along a path by detecting and moving towards a space-apart plurality of stationary LEDs. Of course, many other guidance systems can also be used.
The method and apparatus according to the invention may have a number of different levels of application.
For example, one application is in a system in which no off-board vehicle control system is used. Control of the vehicle is limited to telling the vehicle where to go, starting the vehicle along the guidance path and stopping the vehicle when it reaches its destination. Such a system provides a flexible, self-sufficient AGV at a relatively lower cost than prior art systems having much less flexibility.
Another application would include the use of the method and apparatus of this invention in combination with an off-board system controller which communicates with a plurality of vehicles to give the AGVs a greater degree of self control and to add greater flexibility to the design and lay-out of the AGV path. The off-board system controller handles order management, host interfacing, traffic control and similar duties while, according to the invention destination and certain AGV functions are carried out separately.
The basic principle behind the invention is to provide certain information at logically-predetermined spaced-apart points along the vehicle path to an AGV vehicle. The information is delivered to the AGV from a stationary point. Delivery is made by means of a reader mounted on the AGV which passes across the stationary point and, while so doing, receives information which is interfaced with the AGV controls to provide a predetermined response.
Similar functions have been provided with much less flexibility and efficiency by the use of several prior art methods. One such method involves the use an optical reader mounted on an AGV which reads bar codes painted onto or otherwise adhered to the floor along the path followed by the AGV. Such optical sensing devices provide only relatively limited capacity for information transfer and must be replaced when worn or when a change in the information to be transmitted is required. Such systems are particularly sensitive to soiling, wear and misalignment between the bar code strips and the optical reader.
Another system used in the prior art is a series of metal plates arranged in a pattern along the AGV path. A magnetic reader on the AGV senses the magnetic fields generated by the metal plates in a particular series pattern as the AGV moves across the array of metal plates. As with the above-described optical system, the amount of information which can be transmitted by this manner is relatively limited. The arrangement of the magnets must be manually changed whenever a change in the information to be transmitted is required. Of course, this system is particularly sensitive to magnetic interference from other sources.
Another prior art type of system includes the stacking of magnets with the north-south orientation varied to generate an output having a particular cumulative magnetic angular orientation. This orientation is sensed by a reader on the AGV. This system suffers from essentially the same limitations as described above.
The method and apparatus according to this invention makes novel use of components which are already known. One of the components is best described as a passive programmable transducer for dynamic coding. This particular type of transducer and its associated reader/writer is described in detail in U.S. Pat. No. 4,459,590. In its prior art use, the device is attached to articles, such as TV or automobile chassis, which are moving along an assembly line, or to stock items being stored and/or retrieved in a warehouse environment. As items to which the transducer is attached move along a predetermined path, they pass within close proximity of a stationary reader/writer which can receive information from the transducer. There are a number of significant features unique to this type of apparatus. First, the transducer is totally passive. The transducer can receive and store information in digital form without contact or electrical connection and without an electric supply. The reader/writer apparatus can receive the digital information programmed in the transducer by passing over it in close proximity. In another mode, the reader/writer can erase the digital information stored in the transducer and reprogram it with other information. It must be emphasized that these components have heretofore been used by mounting the transducer on moveable items such as automobile chassis and passing the transducers past stationary reader/writers. By so doing, production mapping, automatic assembly, sorting and process control is carried out by delivering information received by the reader to a central computing system and, when necessary, sending programming instructions to the writer which adds and/or replaces information on the transducer.
The method and apparatus according to this invention involves the adaptation of the components described above to a completely new environment for a different purpose.